The main reason why overhead lines are vulnerable to lightning strike and dirty flashover is that the pin insulator of the line is polluted and moisture-absorbing in rainy days, and the insulation level is reduced, so that the pollution flashover and breakdown cause line failure.The pin type ceramic insulator can continue to operate sometimes in fine weather after cracking or severe injury.But in light rain, fog weather, the insulation suddenly dropped, causing line failure.In addition, when the needle type ordinary ceramic insulator has a slight crack, even if the line inspector holds a telescope, it is difficult to find the defect, which leaves a hidden danger for the line and increases the unsafe factors of the line operation.
The function of insulator is to realize electrical insulation and mechanical fixation, for which a variety of electrical and mechanical properties are required.If under the specified operating voltage, lightning overvoltage and internal overvoltage, no breakdown or flashover occurs along the surface;Under the specified long-term and short-term mechanical load, no damage and damage;In the specified machine, electrical load and various environmental conditions after long-term operation, no obvious deterioration;An insulator's hardware that does not produce significant corona discharge under operating voltage, so as not to interfere with radio or television reception.Because insulators are widely used devices, the interchangeability of the connecting hardware is also required.In addition, the insulator technical standards also require insulators to be tested in various electrical, mechanical, physical and environmental conditions according to different models and operating conditions, so as to check their performance and quality.